PVC or T18 steel soffits: what should you check at the eaves?

A soffit finishes the underside of the eaves and limits access beneath the roof. It shields components from dirt and, with suitable openings and guards, helps keep birds out. Preserve the airflow paths required by the roof design. Closing them can compromise the performance of the roof even if the underside looks tidy.

Locate the gutter, fascia and ventilation inlet. Mark lighting cables and parts likely to need maintenance. The soffit should allow access to them. If even a small repair requires removing an entire run of panels, servicing will cost more.

Lightweight PVC panels are available with matching mounting profiles and ventilated sections. Colour and texture vary. Check the permissible support spacing, laying direction and expansion clearance. A long panel held rigidly at both ends may buckle or pull its joints apart as the temperature changes.

Select a panel intended for outdoor exposure and the proposed orientation. Cold material and unsuitable cutting tools increase the risk of damaged edges. Follow the cutting and fixing instructions and use compatible system trims for the ends and joints.

T18 gives the underside a pronounced ribbed pattern and a relatively stiff section. Its ribs need more space than shallow soffit panels and are more prominent from below. Check clearance and how the sheets terminate at the wall and fascia. Cutting sheets to the width of the overhang addresses only one dimension.

Choose steel thickness, coating and supports together. The fixings must transfer wind forces on the soffit. Inspect the face that will be visible after installation. The reverse coating on standard roofing sheet may look different from the finish you want. Request a sample with the specified coating on both sides.

A ventilated roof needs both inlets and outlets sized for the chosen build-up. Perforated panels can admit air, but use their actual free ventilation area. A count of holes in a photograph gives no reliable figure. Mesh and pest guards can reduce the available opening.

Ribs in a solid T18 sheet do not by themselves make an air inlet. Gaps at a flashing may be closed or fail to reach the ventilation channel. Detail the inlet deliberately. Any openings need finished edges and suitable protection against animals while preserving the designed airflow.

The soffit colour can complement the walls and windows without matching the roof exactly. A light finish brightens a deep overhang, while a dark one emphasises its outline. View samples in shade, where the soffit will normally be seen. Roof colour in full sunlight may give a misleading comparison.

Add framing, end profiles, fasteners and ventilation pieces to the material price. Steel sheets also need flashings shaped for the actual junctions. Make sure corners and unusual terminations are included. These details can account for a large share of a small soffit’s total cost.

Inspect alignment, edges and fixings. Check for loose parts and ensure the panels can move as required. Look for obstructed drain holes or air inlets. Cables and light fittings must suit the chosen material. Heavier equipment needs its own support rather than hanging from the sheet alone.

Remove protective film within the specified time and clear away metal swarf. Keep service points accessible. A well-fitted soffit should remain quiet in gusts. The choice between PVC and T18 depends on how the framing, ventilation and visible finishes work together at the eaves.